I will show you how you find out if a website of your choice is using cookies. If the result is positive, you also find out which cookies are being used and what's their purpose.
In case you just upgraded your iOS powered device to iO7 or any other version and now this device runs slower than it used to, this resetting of the device procedure might speed things up.
With time it can happen you have a bunch of installed apps on your Windows Phone 8 powered phone you never use anymore, I suggest you to remove them to free some of the storage.